David Trimble has accused Scottish nationalists of "doing violence" to the partly British identity of every Scot by trying to break up the UK.

The former Ulster Unionist leader told a rally to launch a new anti-independence campaign that every Scot had a dual British identity that was being threatened by the Scottish government's proposals for an independence referendum.

Trimble, who shared the Nobel peace prize in 1998 for his role in the Northern Ireland peace deal, said separatism and Irish nationalism was now waning in Northern Ireland: the most recent study from 2010 showed that support for remaining in the UK had an "overwhelming" four to one majority. Among nationalists, only a third favoured leaving the UK.

"I have no doubt that just as we won the argument there, we can win the argument here again also," he told the Conservative Friends of the Union rally, at the Scottish Tory party's spring conference at Troon, in Ayrshire.

He continued: "I have to say to the Scottish nationalists, by moving through a programme of separatism, by saying we want to drive Scotland out, you are doing violence to the identity of every Scot because there is a British component in the identity of every Scotsman."

Lady Syeeda Warsi, the co-chair of the UK Tory party, told the rally, which was also attended by the Welsh secretary, Cheryl Gillan, and Lord Strathclyde, the Tory peer, that multiple identities were a significant part of being British. She said: "A person's loyalty to Scotland isn't compromised if they're also loyal to the UK."

She said the pro-union campaign should draw inspiration from the anti-AV campaign in the referendum on changing the Westminster voting system, which began by exposing how complicated and unnecessary the AV system was.

"We won [the referendum] by demonstrating how powerful and precious the one-person one-vote system was," she said. The anti-independence campaign "needs to show not just how Scotland would be worse off without the UK but how Scotland would better off in the UK, and how the UK would be better off too."

While the Northern Ireland survey, the annual Life and Times series, has found Irish nationalism is dwindling and a greater identification with being British, comparable surveys in Scotland have found nearly a third of adults do not see themselves as British.

The British social attitudes survey and the Scottish social attitudes surveys found that if voters are forced to choose, 52% of English voters choose British first compared with just 19% of Scots, and 30% of Welsh. Meanwhile, only 37% of Scots saw themselves as both British and Scottish.

The 2010 Northern Ireland Life and Times surveys have shown that 58% of voters in Northern Ireland in 2007 saw themselves, to varying degrees, as both British and Irish. Asked to make just one choice, 37% saw themselves as British, 26% Irish, and 29% Northern Irish, with 3% choosing "Ulster".

Ruth Davidson, the Scottish Tory leader, told the rally that multiple identities were an essential part of Britishness. "At its simplest, this debate is about who we are, and who we want to be. It's about nationality, identity and belonging.

"It's about being Scottish and British – and not having to choose between the two, about not letting Alex Salmond take one of them away. He can't. He won't. Because we won't let him. We will win."

The first minister, who describes himself as an Anglophile, and other senior figures in the SNP have repeatedly insisted that they believe an independent Scotland would continue as a member of the British "family" of nations. It would continue sharing very close economic and social ties, and would be expected to share services and institutions such as the BBC.

Humza Yousaf, the Scottish National party MSP for Glasgow, said: "It is precisely this sort of negative nonsense that is so damaging to the Tory-led anti-independence campaign.

"Lord Trimble couldn't be more wrong about Scotland. Independence is the broad, inclusive and positive option for Scotland, in which the wide range of identities we have in our modern nation – Scottish, British, Pakistani, Chinese, Polish, Irish and many, many more – can all be reflected and celebrated.

"Lord Trimble appears to know as little about modern Scottish identity as David Cameron does."